Issue with deleting uploaded files

I’ve got problem with deleting uploaded files.
When I’m logged as user who uploaded files everything is OK. I click delete and uploaded file is deleted.

The problem is when I want to delete other user’s files when I’m logged as admin. I click delete icon and the file seems to be deleted. After this, when i log through FTP all files I wanted to delete as admin are still on server.

What is more, I don’t have access to them. Only way to delete them is to change CHMOD with PHP, and do it manually.

I’m using PRO Version.

Any clues?

https://www.ads-software.com/plugins/nmedia-user-file-uploader/